The discovery of highly stable organic peracid molecules is critical to the commercialization of detergent formulations containing peracid bleaches. Such peracids have recently been discovered which are highly crystalline and have relatively high melting points. Also, it is highly important for highly stable bleaches to be prepared in a manner which eliminates, or at least minimizes contamination from metals. Metals or metal ions are particularly deleterious to peracids because they catalyze the decomposition of the peroxygen group.
Consequently, the detergent industry requires peracids which are highly stable, have high melting points and are conveniently manufactured in high volume. Because of their high melting points both the peracids and their precursors are typically purified by precipitation or crystallization techniques. Metal ions typically present in the crystallization media become trapped in the peracid crystals and become impurities which reduce the stability of the peracid. The amount of metal ion contamination is directly related to stability of the peracid.
A recent patent, U.S. Pat. No. 4,634,551 to Burns et al describes novel, relatively stable and high melting crystalline amide peracids. Generally, the precursors to these amide peracids, that is, the amido acids, were reported to have been prepared by the reaction of the appropriate acid chloride with the appropriate amine followed by precipitation of the resulting amido acid. Stability of the ultimate amide peracids generated via this method are affected not only by metal contamination but also by the chloride impurity. Attempts to purify the peracid has proven inadequate to economically remove metals and chlorides. Even purification of the amine precurser is not adequate to provide an economical product of sufficient purity for use in preparing the peracid.
The peroxyacids found in U.S. Pat. No. 4,634,551 are represented by the the formula ##STR1## where in R.sup.1 is selected from the groups consisting of alkyl, aryl or alkaryl radicals containing from about 1 to about 14 carbon atoms, R.sup.2 is an alkylene group containing from 2 to 14 carbon atoms and R.sup.3 is H or an alkyl, aryl or alkaryl group containing from 1 to about 10 carbon atoms, the total number of carbon atoms being from about 10 to about 20.
There is needed a process for the manufacture of large quantities of alkyl mono amido esters with a high degree of selectivity so as to minimize the simultaneous production of diamido compounds. In one effort to minimize the amount of diamido ester, a large excess of the diester is employed. This requires the movement and handling of large amounts of material because the mole ratio of diester to amine needed for improved selectivity to produce the desired mono amido ester is from 5:1 to 10:1.
The reaction of an alkyl amine with, for example, the diester of adipic acid is well known as in U.S. Pat. No. 3,417,114 to Kueski. It is noted therein that esters of mono-, di, tri, or tetracarboxlyic acids may be employed wherein the resulting amide may contain one or more ester groups, depending on the extent to which the ester groups are converted to amide groups. However, no indication is given as to how to provide a selective reaction to produce a mono amido ester of a dibasic acid.
The production of amides by reaction in a column is described in U.S. Pat. No. 3,324,179 to Scholz et al. This patent discloses the reaction of four carbon fatty acids with alkylamines wherein the amine reactant is in excess or at least in stoichiometric amounts. Reflux ratios in the range of 2:1 to 30:1 are disclosed.
The production of methyl formamide by the reaction of ammonia and methyl formate in a reaction column is disclosed in U.S. Pat. No. 4,659,866 to Kaspar et al. It is reported that virtually quantitative conversion to the amide is provided in a continuous process.
Diamides are prepared in high purity according to U.S. Pat. No. 3,296,303 to Nemec et al by the reaction of a secondary amine with a diacid or diester wherein the diester is derived from selected ethylene or propylene glycols. The amidation step is conducted by employing the amine in a ratio with the ester or acid of at least 2:1. The process seeks to avoid the production of a mixture containing mono ester amides.
Amides are also produced in the presence of water at relatively low temperatures by employing catalysts according to U.K.1,108,395. There is reference to conducting such reactions in a column. Amides are prepared at temperature of less than 30.degree. C. with ion exchange resins, either strongly basic or strongly acid.
Although considerable work has been done in the art of preparing amides, the provision of a selective reaction of an amine with a dibasic acid to provide a high proportion of mono amido esters of such dibasic acids has not heretofore been discovered. In the production of large quantities of such material it is vital to reduce the amount of unwanted production of diamides to provide an environmentally sound mass production process.
Attempts to provide the mono amido ester of dicarboxylic acids has resulted in a relatively low yield of the desired product. The above mentioned patent to Kuceski indicates, recovery from a catalyzed reaction of about 40% by weight of the mono amido ester of adipic acid, based upon the weight of the original starting material. Other attempts to provide such product from dimethyl adipate improved over the result of Kuceski only by employing large excess of diester in the reaction mixture. Excess diester, on a molar basis, of up to 10:1 over the amine reactant in a typical batch type reaction was required to obtain up to 93% recovery of the mono amido methyl ester of adipic acid. However it is desirable to use more economical processes than can be achieved with such a large excess of starting material.